[Hallicrafters] sx42 assistance

[brian.crawford at shaw.ca]

A Merry Christmas and Happy New Year to all and especially those that
have given so freely of their time and advice to assist me in my sx42
restoration.  However, it is far from over yet so I continue to ask your
indulgence, and worse yet I have two more Hallicrafters wanting to sneak
up from the floor onto the workbench (S40 & 51R10A).

So, for those of you that feel like Santa here's my problem.
The plate and grid voltages on the 7H7 1st Limiter are very low.  When I
turn the unit on the voltage rises to about 300 (on the plate and
slightly less on the grid) and then gradually (5-8 seconds) settles down
to about 100 & 80 volts respectively (should be 200 and 180).  The
cathode has about 0.4V on it (should be > 1 depending upon band).  Both
7H7s test OK on my tester (and I have sub'd them with each other -
reliable test eh?)

In trying to trace the circuit I find that my circuit does not match any
of the 5 different schematics I have.  It seems like a mixture of a
couple of different ones.  The ones I have are Sams 4814-6, Rider Pages
17-7,8 and 3 others marked 89D210K, 89D210F and 89D257G (both halves of
the 6H6 are in use so that limits the choices a bit).  It seems closest
to the 89D257G but the cathode connection only has a 33 ohm resistance
to ground which is like Riders.  I have tried a couple of minor
"re-wirings" to match one or other but continue to have low voltages.

I have measured the resistance across the IF coupling-coil which showed
about 120k resistance which seems odd as there is a capacitor in series
in the "can" but disconnecting it from the other 7H7 tube socket made no
difference to the reading (probably should have disconnected it on the
1st limiter side to ensure something is not haywire inside -short to
ground?)

By the way if any one has a very readable 89D257G schematic I could beg,
borrow or buy, the one I have is a little too small and a little blurry
to read even under a magnifying lens (well over 50 so can't expect too
much).

Thanks, and have a good holiday all.
Brian